Paula Q. Barrett

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Research Interest(s)

Regulation of low-voltage activated T-type Ca2+ channel activity by kinases and heterotrimeric G-proteins and their roles in physiological responses.

Research Description

Calcium channel regulation and the control of cell function

Intracellular calcium is a universal signal mediating the actions of many hormones. During cell activation, intracellular calcium rises dramatically, as the activities of calcium entry pathways are increased. Voltage-gated calcium channels prominently regulate the entry of calcium into cells. Their activity is regulated by voltage, and hormones. A subclass of these channels, the low-voltage-activated, T-type, calcium channel regulates action potential frequency in excitable cells and provides the calcium necessary for cell activation in non-excitable cells that maintain a relatively static negative membrane potential.

Low-voltage-activated calcium channels have been implicated in the pathogenesis of arrhythmias, epilepsy, diabetes, hypertension, and in the progression of congestive heart failure. Our laboratory is interested in delineating the signaling pathways that control the activity of this channel type and focuses on defining the molecular mechanisms underlying regulation and the relationship of channel activity to physiological function.

Regulation and role in aldosterone secretion
Using a combination of whole cell and single channel electrophysiologcial recording techniques, we have shown that both the activation of a kinase, calcium-calmodulin-dependent protein kinase II (CaMKII), and the activation of a G protein, Gi, induces a hyperpolarizing shift in the voltage-dependence of activation (opening) of the T-type calcium channel that results in an increase in channel current at negative potentials. We are currently using molecular biological techniques and clonal cell lines that express the T-type calcium channel to identify the sites of phosphorylation, the activating G protein subunit, and the sites of G protein interaction that underlie the stimulatory changes in channel gating. How these mechanisms interact during Angiotensin II stimulation and their physiological significance to the secretion of aldosterone is being pursued.

Regulation and role in insulin secretion
In neonatal and fetal tissues, CaMKII beta isoforms are abundantly expressed. Using a combination of immunogloical and molecular approaches we have identified a novel isoform of CaMKII in an insulin secreting cell line. We are investigating the consequences of activation of this novel isoform of CaMKII to the regulation of intracellular calcium, the modulation of T-type calcium channel activity and the secretion of insulin during physiological glucose stimulation.

Chen X, Bayliss D, Fern R, Barrett P. A role for T-type Ca2+ channels in the synergistic control of aldosterone production by ANG II and K+. The American journal of physiology. 1999;276(5): F674-83. PMID: 10330049